Why not have a section where people looking to make money could talk about their set of skills and actually allow readers to benefit from a service they potentially needed but didn't know where to look for?

Let's say most of those services would not have a website before hand ( no links to throw around except maybe for a contact email to be displayed in the thread ) and pay would be delivered upon completion of the deal agreed on? To be fair to the other party one(mmg?) could also put a limit on the amount of money that could ever be owed at one point or another (50$)? these steps alone should help....